Effect of rearing density on growth, survival and reproductive performance of domesticated Penaeus monodon

The growth, survival and reproductive performance of tank-reared, 2nd generation domesticated Penaeus monodon, originating from founder stocks collected from a population off the coast of Weipa (12°48′, 141°32′), Gulf of Carpentaria, Queensland, Australia, were compared when reared at a standard density for maturation (SD) (approx. 3 individuals m− 2) and a low density for maturation (LD) (approx. 1 individual m− 2). Growth and survival of the shrimp reared at the two densities in 10·000 L tanks (3.6 m dia.; 10 m2 tank-bottom area) were assessed from 5.5 months of age through to 10.5 months of age. Reproductive performance of shrimp in the two density treatments was assessed from 10.5 months of age for two moult period's post-ablation under standardized conditions. The weight of the female shrimp at 10.5 months of age (mean ± S.E.) was significantly greater at LD (131.2 ± 4.9 g) than at SD (120.3 ± 2.5 g). No difference in 10.5 month weight was found between males at LD (90.9 ± 2.2 g) and SD (87.4 ± 1.5 g). Significantly more spawnings were produced at LD (2.2 ± 0.2 ablated female− 1; 3.4 ± 0.6 spawning female− 1) than at SD (1.3 ± 0.2 ablated female− 1; 2.4 ± 0.6 spawning female− 1). The percentage of spawnings that hatched (LD 87.2 ± 5.1%; SD 61.8 ± 6.6%), eggs per spawning (× 103) (LD 231 ± 21; SD 148 ± 16) and nauplii per spawning (× 103) (LD 39 ± 8; SD 16 ± 3) were also significantly higher at LD. Hatch rates per spawning were low and did not differ between LD (19.0  ± 2.7%) and SD (16.8 ± 2.4%). No significant differences in spermatophore weight (LD 0.19 ± 0.02 g; SD 0.20 ± 0.01 g) or sperm count (× 106) (LD 6.25 ± 0.77; SD 8.44 ± 1.15) were found between males at the two densities. While egg and nauplii production (× 103) were significantly higher at LD than SD when expressed per female (LD 434 ± 115 eggs, 73 ± 26 nauplii; SD: 160 ± 44 eggs, 17 ± 7 nauplii), no significant difference was found when expressed per m2 tank-bottom area of the maturation tanks (LD 272 ± 67 eggs, 46 ± 21 nauplii; SD 271 ±109 eggs, 29 ± 15 nauplii). Our results found that lowering the maturation density of tank reared P. monodon stocks from approx. 3 individuals m− 2 to 1 individual m− 2, over a 5 months maturation period, improved growth of females and reproductive performance when expressed per spawning or per female. However, no significant increases in egg and nauplii production were obtained by reducing the maturation density when expressed per tank-bottom area.